package com.bit.java;

import java.util.Scanner;

public class Test2 {
    public static int Fun(int n) {
        if(n == 1 || n == 2) {
            return 1;
        }
        return Fun(n - 1) + Fun(n - 2);
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int ret = scanner.nextInt();
        System.out.println(Fun(ret));
    }

}
